Imaging system

ABSTRACT

A woven pile brush for the brush development of latent electrostatic images is provided with both nonconductive and conductive pile fibers. The conductive pile fibers are shorter than the nonconductive fibers, and thus, the shorter conductive fibers can function as a development electrode while avoiding contact with the latent electrostatic image carrier.

United States Patent Inventor Appl. No.

Filed Patented Assignee I Thomas w. Solarek Fairport, N.Y. 889,072

Dec. 30, 1969 Oct. 19, 1971 Xerox Corporation Rochester, NY.

IMAGING SYSTEM 13 Claims, 4 Drawing Figs.

U.S. Cl.

Int. Cl Field of Search 56] References Cited UNITED STATES PATENTS 3,058,444 10/ l 962 Sugerman et al. 117/ l 7.5 3,098,765 7/ 1963 Keller et a1. l 17/ l 7.5 3,399,652 9/1968 Gawron ll7/ 17.5

Primary Examiner-Even C. Blunk Assistant Examinerl. Kenneth Silverman Anorneys- Paul M. Enlow, James J. Ralabate, Albert A.

Mahassel, Peter H. Kondo and Boris Haskell ABSTRACT: A woven pile brush for the brush development of latent electrostatic images is provided with both nonconductive and conductive pile fibers. The conductive pile fibers are shorter than the nonconductive fibers, and thus, the shorter conductive fibers can function as a development electrode while avoiding contact with the latent electrostatic image carrier.

PAIENTEnnm 19ml INVENTOR W. SOLAREK BY v fimM

ATTORNEY THOMAS IMAGING SYSTEM BACKGROUND OF INVENTION In xerography and relatedarts, a'latent electrostatic information image is formed on anelectrically insulating carrier. In one form of xerographic recording, the latent image is formed optically byfocusing alight image on a photoconductive plate, and creating a differential electrostatic charge pattem' correspondingto the light image. The resultant latent image is developed by the application'of tonerparticles, whereby the particles are caused'to adhere electrostatically either to the portions of the plate exposed to light, or to the portion notso exposed, and the adhered'toner particles are then transferred imagewise to an image receiving or record sheet.

A number ofr'ways are knownin the art for obtaininga proper distribution of toner particles over the electrostatic latentirnagecarryingsurface of the photoconductive plate, so as to obtain suitable development of thelatent image into visible form. One of the well recognized development methods is often referred to as brush development, in whicha furbrush moves in contact'with a supply of toner-particles and brushesv the particles across the electrostatic image carryingsurface. It is also known that certaintypes of images, particularly those having large expanses of light and dark areas, can be developed withmore uniform effects in the presence of a development electrode positioned closelyadjacent to the electrostatic image-carrying surface during the period of application of the toner particles thereto.

SUMMARY OF THE INVENTION Thepresent inventionis directed to an improvement in the brush development-of 'xerographic electrostatic images, and more particularly the inventionis directed to a fabricated brush for this purpose. Ingeneral, this development brush is fonned from a woven pile material, whosepile tufts include a mixture of electrically nonconductive and electricallyconductive fibers. The conductivefibers of thepile' are made shorter than thenonconductive fib'ers. Thus in operation, the brush' can belocated relative to theelectrostaticimage-bearing surface so that the nonconductive fibers brush against the charge pattern surface to distribute tonerparticles thereover, while the conductive fibers are spaced a short'distance from the charge pattern surface and can function as a development electrode. In this manner, the properties of the two types of fibers can be selected independently, to provide appropriate electrical and physical properties for the two functions to be performed. For example, the longer fibers can be selected to provide. optimum triboelectric properties, fiber density, and fiber stiffness for the distribution of toner particles, while the shorter fibers can be selected to function optimumly' as a development electrode without regard to the properties required of the longer fibers. For example, the shorter fibers can be formed of steel threads, whose stiffness and-abrasiveness might scratch and injurethe photoconductive electrostatic image-bearingzsurface, if they were caused to contact said surface.

It is therefore one object ofthe present invention to provide forimproved. brush development of electrostatic latent images.

Another object of the invention is to provide an improved brush for the development of electrostatic latent images.

Andstill another object is to provide an improved brush for thedevelopmentof electrostaticlatent images, having both nonconductive-and conductive pile fibers,'wherein the conductive fibersare shorter than the nonconductive fibers.

Other objects and advantages of the present invention will become apparent to those skilled in the art, from a consideration of the following detailed description of one embodiment of the invention had in conjunction with the accompanying drawings.

DESCRIPTION OF DRAWINGS FIG. 1 is a schematic illustration of a xerographic apparatus, incorporating brush development of the electrostatic latent image;

FIG. 2 is a perspective view of a pile brush embodying the present invention;

, FIG. 3 is an enlarged cross-sectional detail of the pile brush of FIG. 2, taken along the line 3- 3 of FIG. 2'; and FIG. 4 is a further enlarged detail of a composite yarn utilized in fabricating the pile brush of FIG. 2 and 3;

DETAILED DESCRIPTION FIG. 1 schematically illustrates a well-known xerographic process and apparatus for electrostatically photocopying documents. Drum 10 isprovided with permanent photoconductive layer ll over its cylindrical surface. The photoconductive layer 11 is commonly formed of selenium, and presents a relatively low electrical resistance when illuminated with' light and a relatively high resistance when not illuminated. A plurality of operational stations are positioned aboutthe periphery of the drum as follows: an optical station is provided at 14, for focusing an optical image on the photoconductona developing station is provided at 19, an image transfer STATION is provided at 24, a drum-cleaning station is located at 30,. a general-illuminating station is located at 31, and it is followed by a general-charging station at 32.

Assuming that the drum 10 is rotating in the direction of arrow'A, and assuming that the drum surface is clean and uniformly charged with an electrostatic surface charge, an image of a portion of document 13 is focused by optical system 12 on the photoconductor surface 11 at station 14. As the drum advances in the direction of arrow A, successive-portions of the document 13 are focused on successive portions of thephotoconductor 11. The portions of photoconductor 11 that are illuminated with light become conductive during the illumination period, causing a discharge to ground of the corresponding electrostatic charge portion on the surface of the photoconductor, and resulting in a latent electrostatic image of document 13 on the surface of drum 10.

The electrostatic latent image is advanced to the developing station 19,-where a housing l5 contains a charge of electroscopic toner particles 18, and roll 16 having a pile brush 17 on its surface. As roll 16 rotates, the pile brush l7 passes through the toner particles and then across the surface of drum 10, distributingthe toner particles 'over the surface of the drum. The toner particles adhere to the drum in areas containing a residual charge, but not inthe uncharged areas, resulting in development of the electrostatic image corresponding to document 13.

At station 24, this image is transferred to image-receiving web'20L'Web 20 is drawn'from supply roll 21 and is guided in contact with drum l0 for-a short distance by guide rolls 22 and 23.Transfer of the toner particles constituting the developed image may be aided by an appropriate electrical field or charging of the web 20, as is well understood in the art. After theimage is transferred to the web 20,the web may be passed through a heater 25 to fuse the toner particles to the web, and the web is guided by roll '26 to-a delivery station.

After the image transfer operation, residual toner particles are-removed from the surface of drum 10 by brush 27 at station 30. Then the photoconductive surface 11 is exposed at 31 to uniform illumination by lamp 28,'to erase any residual electrostatic image. Before returning to the optical exposure station, the surface of the photoconductor is exposed to a general corona discharge by electrode 29 at station 32, to provide a uniform electrostatic charge over the photoconductive surface 11 and thereby enable electrostatic optical recording of an image of the document 13.

The brush I7 is a flexible woven pile fabric mounted on cylindrical roll 16. Obviously, the fabric could be mounted on a set of guide rolls to traverse any circuit path desired other than the circular one shown. The fabric brush 17 is shown FIG. 2, and comprises a backing 41 and a cut pile surface 42.

The backing 41' is a conventional woven fabric composed of interlaced warp and woof yarns 43, as shown in FIG. 3. The cut pile comprises a separate yarn 44, interlaced with the backing yarns 43 in a manner quite conventional in the manufacture of cut woven pile fabric. It will be noted, however, that the pile yarn 44 is composite of two different fibers, one having a shorter length than the other. In accordance with the present invention, the shorter fibers 45 are electrically conductive, while the longer ones 46 are nonconductive.

In order to obtain the different lengths of fibers within a pile cut, the'original pile yarn is a composite in the form shown in FIG. 4, wherein a straight fiber bundle corresponding to fibers 45 has a second fiber bundle corresponding to fibers 46 serpentinely wound thereabout. This composite yarn as shown in FIG. 4, is used as the pile yarn 44 in weaving the pile fabric 17. After the weaving operation is complete and the pile yarns are cut, the serpentine bundle 46 unwinds itself from the straight bundle 45, and thus obtains a longer length as shown in FIG. 3.

As previously stated herein, the resultant longer pile fibers 46 are selected to be electrically nonconductive and to provide appropriate physical and triboelectric properties to dust the electrostatic image-bearing surface 11 of cylinder uniformly with toner particles 18. On the other hand, the shorter fibers 45 of the pile tufts are selected to be electrically conductive and thereby function as a development electrode. It is apparent, therefore, that in use the surface of brush 17 may be located so that only the longer fibers 46 touch the photoconductor surface 11 of cylinder 10, and the physical properties of the shorter fibers 45, such as stiffness and abrasiveness, which could be deleterious to the surface 11, are not material, It is also apparent that to provide the development electrode function, not all of the pile yarns used to manufacture the pile fabric 17 need necessarily be the composite type of FIG. 4, so that many of the pile tufts may be formed from yarns composed solely of the dusting type of fiber 46. And it is further apparent that through the roll 16, the development electrode conductive fibers 45 can be biased to a desired electrical potential appropriate for the parameters of operation of the system.

In the preferred form of the present invention, the conductive fibers are steel and the nonconductive fibers are rayon. The steel fiber bundle 45 is composed of steel fibers of about 0.12 denier, and the denier of the bundle is approximately 12. The rayon bundle 46 is composed of fibers having a diameter of approximately 20 microns, and the denier of the bundle is approximately 150. The ratio of steel to rayon pile fibers is preferably approximately one to one by volume; and the preferred pile height for the rayon fibers 46 is approximately 0.6 inch, while for the steel fibers 45 it is approximately 0.4 inch. It is understood however that the present invention is not limited to the particular pile fiber materials recited, since they are presented only as exemplary and numerous other conductare electrically conductive, said first pile fibers being all of substantially one pile height, said second pile fibers being all of substantially a second pile height, and said second pile height being less than said first pile height.

2. A brush as set forth in claim 1, wherein said pile fabric is a woven cut pile material.

3. A brush as set forth in claim 2, wherein said second pile fibers are metallic filaments.

4. A brush as set forth in claim 2, wherein said first pile fibers are synthetic filaments.

5. A brush as set forth in claim 4, wherein said second pile fibers are metallic filaments.

A a brush as set forth in claim 5, wherein said synthetic filaments are rayon and said metallic filaments are steel.

7. In an electrostatic xerographic apparatus having a brush for the application of electroscopic toner developer particles to the surface of an electrostatic image-bearing surface, the improvement wherein said brush has a pile formed from two different fibers, a first of said pile fibers all having substantially the same pile height and being substantially electrically nonconductive and triboelectric for dusting said toner particles over said surface, the second of said pile fibers all having substantially the same pile height and being electrically conductive to provide a development electrode, and the pile height of said second fibers being less than the pile height of said first fibers.

8. In an apparatus as set forth in claim 7, said pile fabric being a woven cut pile material.

9. In an apparatus as set forth in claim 8, said second pile fibers being metallic filaments.

10. In an apparatus as set forth in claim 8, said first pile fibers being synthetic filaments.

11. In an apparatus as set forth in claim 10, said second pile fibers being metallic filaments.

12. In an apparatus as set forth in claim ll, said first pile fibers being rayon filaments and said second pile fibers being steel filaments.

13. In an apparatus as set forth in claim 7, said brush being positioned relative to said surface to place said first pile fibers in contact with said surface and said second pile fibers closely adjacent to but spaced from said surface. 

1. A pile fabric brush having first pile fibers that are electrically substantially nonconductive, and second pile fibers that are electrically conductive, said first pile fibers being all of substantially one pile height, said second pile fibers being all of substantially a second pile height, and said second pile height being less than said first pile height.
 2. A brush as set forth in claim 1, wherein said pile fabric is a woven cut pile material.
 3. A brush as set forth in claim 2, wherein said second pile fibers are metallic filaments.
 4. A brush as set forth in claim 2, wherein said first pile fibers are synthetic filaments.
 5. A brush as set forth in claim 4, wherein said second pile fibers are metallic filaments. A a brush as set forth in claim 5, wherein said synthetic filaments are rayon and said metallic filaments are steel.
 7. In an electrostatic xerographic apparatus having a brush for the application of electroscopic toner developer particles to the surface of an electrostatic image-bearing surface, the improvement wherein said brush has a pile formed from two different fibers, a first of said pile fibers all having substantially the same pile height and being substantially electrically nonconductive and triboelectric for dusting said toner particles over said surface, the second of said pile fibers all having substantially the same pile height and being electrically conductive to provide a development electrode, and the pile height of said second fibers being less than the pile height of said first fibers.
 8. In an apparatus as set forth in claim 7, said pile fabric being a woven cut pile material.
 9. In an apparatus as set forth in claim 8, said second pile fibers being metallic filaments.
 10. In an apparatus as set forth in claim 8, said first pile fibers being synthetic filaments.
 11. In an apparatus as set forth in claim 10, said second pile fibers being metallic filaments.
 12. In an apparatus as set forth in claim 11, said first pile fibers being rayon filaments and said second pile fibers being steel filaments.
 13. In an apparatus as set forth in claim 7, said brush being positioned relative to said surface to place said first pile fibers in contact with said surface and said second pile fibers closely adjacent to but spaced from said surface. 